A communication system includes a first switch that exchanges information with a neighboring switch by a preset routing protocol to form a forwarding table and that references the forwarding table to forward a packet. The communication system also includes a second switch that forwards the packet in accordance with an instruction from a preset controller, the controller that gives the instruction to the second switch, and an integrated controller. The integrated controller instructs the controller to forward the packet along a path specified for the second switch and to generate a virtual network formed by a virtualized switch as the first switch. The information is exchanged between the second switch mapped to the virtual network and the first switch by the preset routing protocol to cause the packet to be forwarded along a pre-calculated path.